Diamond is an excellent electrical insulator; however, it is known that diamond can be made to conduct electrical current when illuminated with a beam of electrons. One of the applicants (Lin) has patented a diamond switch (U.S. Pat. No. 4,993,033 issued Feb. 12, 1991) in which a diamond target conducts electrical current in an electrical circuit when the diamond target is illuminated by electrons from an electron emitting surface. The teachings of this patent are incorporated herein by reference.
Field emission electronic devices are well known. In U.S. Pat. No. 5,355,093 issued to Treado and Lin on Oct. 11, 1994, an electronic amplifier circuit was described in which a microwave signal stimulated a gated field emission array to emit a modulated electron beam which in turn illuminated a diamond in a diamond switch to produce an amplified microwave signal in the amplifier circuit. The teachings of that patent are also incorporated herein by reference.
Flat panel display devices are relatively new but they have recently become big business. The January issue of Photonics Spectra predicts that the market for flat panel displays will reach $20 billion by the year 2000. Active matrix liquid crystal display (AMLCO) devices account for about 87% of flat panel display sales in 1995. According to the May 1993 issue of IEEE Spectrum, field emitter devices accounted for 0.1% of the world market in flat panel display devices. Prior art FED devices are described in "Beyond AMLCD's: Field Emission's Displays?" in the November 1994 issue of Solid State Technology which article is incorporated herein by reference.
FIG. 1 describes a typical FED device. Electrons are liberated from emitter tip 2 on cathode plate 4 and the electrons are accelerated (by an electrical potential between cathode plate 4 and electrode layer 10) toward phosphor layer 6 on face plate 8. Voltage applied to gates 12 control electron flow and thus the brightness of individual pixel areas of phosphor layer 6. Phosphor layer 6 and electrode layer 10 are mounted on glass faceplate 8.
Most FED's must be operated at very high vacuum, not only to provide long mean free paths but to maintain a clean environment for the emitters. Cathode plates are typically metals and various techniques have been developed to produce emitter tips in order to increase electron flow from the cathode plate. A serious problem with current FED's is that reverse ion bombardment from the phosphor damages the emitter tips. Another problem is that electric fields near breakdown limits are required for the desired current output resulting in reduced lifetime of the emitter array. Other problems are emission noise and energy spread.
What is needed is a simple device for amplifying an electron beam.